Inhibition of adhesion molecule expression on human venous endothelial cells by non-viral siRNA transfection.

OBJECTIVE: Expression of adhesion molecule receptors on venous endothelial cells crucially influences the fate of venous grafts by mediating leukocyte-endothelium interactions. These interactions include adhesion of leukocytes to the endothelium, followed by transendothelial migration, leading to neointimal hyperplasia (NIH) and finally graft occlusion. Therefore, inhibition of adhesion molecule expression may be a promising strategy to improve the quality of venous grafts. We tested the efficiency of non-viral transfection of human venous endothelial cells (HVEC) with short interfering RNA (siRNA) to specifically down-regulate adhesion molecule expression. METHODS: Primary cultures of HVEC were examined for expression of the adhesion molecules ICAM1, VCAM1 and E-selectin (SELE) after non viral siRNA transfection. Adhesion molecule expression was measured by flow cytometry, real-time polymerase chain reaction and immunoblotting after stimulation with TNF-alpha, an inflammatory cytokine. RESULTS: Non-transfected cells showed a strong increase of adhesion molecule expression following cytokine stimulation (P < 0.01). Upon transfection with specific siRNAs a sixfold decrease in ICAM1 (P < 0.001) and SELE expression and cell positivity (P < 0.05) and a twofold decrease in VCAM1 expression and cell positivity (P < 0.01) P could be observed. SiRNA-mediated gene suppression of adhesion molecules was also reflected by corresponding decreases in adhesion protein and transcript levels. CONCLUSIONS: The expression of adhesion molecules on HVECs can be effectively inhibited by specific siRNAs using a safe, non-viral transfection approach. This is a promising tool to pre-condition venous bypass grafts in order to interfere with endothelium-leukocyte interactions and to prohibit neointima thickening or atherosclerosis, which are regarded to be the most important causes of venous graft failure.

Suppression of ICAM-1 in human venous endothelial cells by small interfering RNAs.

OBJECTIVE: Cardiopulmonary bypass-mediated release of proinflammatory cytokines promotes the transendothelial migration of leukocytes. Among others, intercellular adhesion molecule (ICAM) is essential for this migratory process within the venous bypass graft, which finally contributes to a diminished early patency rate by thickening of the intima. Small interfering ribonucleic acids (siRNAs) are efficient and specific modulators of endogenous gene expression. This study describes the application of siRNAs to suppress ICAM-1 expression on the surface of human venous endothelial cells. METHODS: Primary cultures of human venous endothelial cells were either transfected with ICAM-1 siRNA, with a scrambled control siRNA or cultured without transfection. ICAM-1 expression was analyzed with or without TNF-alpha stimulation by flow cytometry. RESULTS: Upon TNF-alpha stimulation, cells transfected with ICAM-1 siRNA showed a six- to seven-fold decreased ICAM-1 expression compared to untransfected cells or cells transfected with the scrambled control siRNA. CONCLUSIONS: This is the first report that ICAM-1 expression can be effectively silenced by siRNAs on endothelial cells from human saphenous veins. This new technology may render novel therapeutic concepts to reduce early graft failure by protecting venous bypass grafts against early intra- or postoperative leukocyte infiltration.